I run exclusively 87 octane. Higher octane gas is not cleaner and in fact is slightly less powerful than lower octane gas. This is because more alcohol is mixed to give it the higher octane and alcohol is less powerful than gasoline. This is why ethynol cars get less mpg than cars that run on gasoline - alcohol is an inherently less powerful substance.

You will know if you need a higher octain if your car does one of two things: pings or knocks after while your engine is running (gurgling sound) or diesels after you durn it off. If it runs smooth, the octane is just fine. My '02 Thunderbird didn't like 87 octane, and it would run good on about 90. However, I was too cheap to use 90 octane, so I just put up with a slight "gurgling" on acceleration in hot weather. The Jeep JK runs on 87 no problem.

 

I have worked in refineries for 17 years. There are a lot of misconceptions about gasoline.

Higher octane does not mean more powerful. It is a indicator of it ability to resist detonation. Which means it can be compressed more before you get engine knock. An engine designed to run on 87 octane gains no additional power from a higher octane. In fact with computor control and engine knock sensors you may ("MAY," I said) get satifactory performance from a lower octane than recomended.

85 octane is not to be confused with E85 ethanol blend. E85 designates a percentage of ethanol alcohol. The octane of E85 can be 87 or higher.

This next statement will most likely get me some arguments.
"All gasolines are the same". Refineries routinely ship gasoline stocks from one producer to another as each has its needs. I originally thought that that being the case, then each manufacturer alters the gasoline mix with their particular additives.

I found out differient when working at an oil terminal where Sunoco, Gulf, Exxon and some independant gasoline companies were filling their tankers at the same loading rack. At the rear of the terminal were smaller additive tanks labeled with each companies name. I thought "there's the diffierence" until I saw that each tank had the same chemical abstract (CAS) number. So all of the additives were the same. A terminal operator showed me that mixing rate of the additives to the gasoline was the same for each brand.

So, in a nutshell, buy the octane that is recommended at the best price you can find. Gas moves so quickly that nobody has old gas lying in ther tanks.

Biggest warning that I can provide is don't buy gas from a station while it is getting filled up itself from a tanker. The filling process can stir up sediment in the storage tanks and if the station does not have proper filters on their pumps, some can wind up in your tank. Come back a few hours later to allow it to settle.

Now sombody ask me about motor oil.

 

I use 89 in the Jeep. The local stations mostly dont have 87 anyhow, unless i go to someplace like Sunoco.

Oh, i live near an Indian resesrvation, i buy all my fuel there. I have been since i could drive, never had any problems on it. They generally dont carry the 87, and the price beats all the chain stores by quite a bit, so if i am paying for the 2 extra unused octane, it is still cheaper than getting the 87 elsewhere. I run 93 in my bike, in my perception it runs far better on it.... ...of course it isn't exactly stock anymore *L*

 

Uhm... NO!

my brain hurts, it's friday i dont wanna think that much!

 

Jeeps only ask for 87....so far I've driven a 96 Cherokee and this is my 2nd Jeep..JK which is also running on 87. Stop listening to fools who have no idea, that tell you to run 93 because they think higher number is better. Take out ur manual and see what it says. Remember, sometimes, in a long run, using the wrong fuel will hurt your engine.

 

Thanks for your knowledge. I actually carry 4 years of chemisrty in my area, but in medicinal. SO... I always wonder why in COLORADO we get ripped of for lower octane levels vs in Houston, Tx. For example, our highest octane 91 but in Houston it's 93. Both are the same price. I have admit Colorado is nice but little competition on goods.....Thx

 

I nor sure about this answer, but gasolines are formulated for the areas to which they are to be sold.

I'm guessing that maybe Colorado's higher elevations than Texas may affect the requirements for 93 octane for that area.

 

Always use 87 for JK or any other Jeep.

Owner's Manual says the engine is designed to use 87 octane gasoline, and it says NOT to use higher than 87. It says at P. 321, "The use of premium gasoline is NOT recommended". It even says "in some circumstances may result in poor performance..."